And some drugs are OTC or BTC in the US that are prescription in other places.
Not all drugs are intended to treat conditions that laypeople are equipped to self-medicate for. Consider extreme examples to illustrate some of the reasons why: it would be completely crazy for people to attempt to use things like powerful chemotherapy or anesthesia drugs to self medicate. And between these and ibuprofen, there's a bunch of other drugs which could easily be harmful to the user (or the purchaser's dependents) if used under a layperson's unguided judgement.
I think this can be even more important in the US where people have a strong incentive to self-medicate without consulting a doctor.
Acetaminophen does have risks, but they are relatively mild and unlikely compared to the spectrum of drugs we're talking about, treats a condition that is extremely easy to self-diagnose: pain.
Not all drugs are intended to treat conditions that laypeople are equipped to self-medicate for. Consider extreme examples to illustrate some of the reasons why: it would be completely crazy for people to attempt to use things like powerful chemotherapy or anesthesia drugs to self medicate. And between these and ibuprofen, there's a bunch of other drugs which could easily be harmful to the user (or the purchaser's dependents) if used under a layperson's unguided judgement.
I think this can be even more important in the US where people have a strong incentive to self-medicate without consulting a doctor.